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MAPPING FROM NON-METRIC SMALL-FRAME PHOTOGRAPHS
USING MULTI-MODEL PHOTOGRAMMETRY
Keld S. Dueholm
Associate professor
Institute of Surveying and Photogrammetry
Technical University of Denmark
Commission V
ABSTRACT:
Multi-model photogrammetry eliminates the need for specialised metric cameras. Geologists, architects and
other scientists can use their own standard 35 mm or 70 mm camera for photogrammetry. Photographs are
taken with a hand-held camera from terrestrial stations, helicopters, light planes or boats. The small-frame
photographs are set up in an analytical plotter where multiple stereoscopic models are simultaneously
orientated. Control points are measured in aerial photographs. The scientists interpret, collect and compile
data continuously across the model boundaries. Accuracies are better than 20 microns at the photo scale.
The multi-model method is illustrated by examples from geological mapping of steep mountain sides in
Greenland, vertical coastal cliffs in Faroe Islands and stone quarries in India and from architectural
measurements in Japan.
KEY WORDS: Photogrammetry, Non-metric cameras, Geology, Geomorphology, Architecture.
1. INTRODUCTION
Photogrammetry is a complicated technology that
uses expensive instruments and specialised cameras.
Projects typically require photogrammetric experts.
Multi-model stereo restitution (Dueholm, 1990) remo-
ves some of these barriers and allows photogramme-
try to be used by geologists, geographers, architects,
archaeologists and civil engineers. These professio-
nals have a growing need for accurate three-dimen-
sional quantification and analysis in relation to the
use of new software tools such as geographical infor-
mation systems and computer aided modelling and
design programmes.
In geology, increasingly advanced computer model-
ling programmes are used to simulate the dynamics
of geological processes in order,for example, to impro-
ve the prediction of petroleum recovery from reser-
voirs. The calibration of modelling programs requires
detailed and accurate three-dimensional data which
are surveyed where geological structures crop out on
the surface of the earth. Exposures on steep moun-
tain sides are a very valuable source of geological in-
formation, but they are also extremely difficult to
quantify by traditional mapping and field survey pro-
cedures.
In geomorphology, the intensified study of climatic
changes involves detailed investigations to be carried
out in often remote arctic environments and includes
comparison of different landscape elements on a time
scale of days, months or years. Also, these investiga-
tions are difficult to carry out by conventional met-
hods based on preexisting topographic maps or verti-
cal aerial photographs.
Documentation of historical buildings is a task that
has interested photogrammetrists over the years. In
the near future, thousands of town renovations are to
be carried out in Europe. Especially in Eastern Eur-
opean countries, a large amount of documentation is
needed. Furthermore, three-dimensional maps are
required for new computer information and design
systems where urban areas or individual buildings
are spatially displayed from any desired angle of vi-
ew. The use of such tools involves a detailed three-di-
mensional survey of house facades in project areas.
While photogrammetry is an exellent tool for three-
dimensional surveys, standard aerial photogramme-
try is of little value in the survey of steep mountain
sides or building facades. Besides, traditional terres-
trial and close range photogrammetric methods are
too complicated and inefficient to be used by persons
without photogrammetric training.
Multi-model stereo restitution includes the advanta-
ge of free movement between stereoscopic models of
different scales and angles of view and provides a
versatile use of small-frame non-metric cameras. The
method is developed in a cooperation between the In-
stitute of Surveying and Photogrammetry at the
Technical University of Denmark and geologists at
the Geological Survey of Greenland and the U. S. Ge-
ological Survey, Geologic Division, Denver, Colorado.
Prototypes based on the Kern DSR15 analytical plot-
ter are installed at the Technical University of Den-
mark and the U. S. Geological Survey.
2. THE MULTI- MODEL METHOD
In traditional photogrammetry a pair of overlapping
photographs are used to create one stereoscopic mo-
del. Multi-model stereo restitution uses many stereo
pairs simultaneously to create a coherent block of
models (multi-model block). The operator moves free-
ly between the images and has the perception of one
large stereoscopic model covering the photographed
terrain or object. An automatic model change occurs
whenever the floating mark is moved across the ima-
ge frame line of either of the two photographs of the
current model. The floating mark moves to the same
point in the neighbouring model across the frame
line.
The photographs in a multi-model block need not be
on the same scale or taken from the same angle of
